A caisson subsea completion system mounts the subsea tree components and a caisson wellhead in a large diameter caisson which is secured to a caisson guide frame at the sea bed. The caisson extends downwardly from the sea floor or mudline and protects components by positioning them below the seafloor inside the caisson safe from icebergs, anchors, fishing nets and the like. Thus, it is necessary for a caisson completion system to provide a slim profile subsea valve for fitting within the caisson. Ball valves have normally been provided in the past for fitting within the casing, because ball valves normally having minimal space requirements.
The caisson typically has a large diameter, such as 36 inches. The valve including a valve actuator must be positioned within the I.D. of the caisson. The valve is normally positioned within a valve block which provides for standard single, dual, or triple string tubing runs. Further, it is desirable that the tubing string does not have axially offset portions which might provide obstruction to wireline tools which may pass through the valve.
While gate valves have in most instances not been provided for a caisson type valve, some designs of gate valves have been utilized. In such cases, however, the actuator for the gate valve has been mounted externally of the casing in which the gate valve has been mounted and has not provided a compact design.